Biomedical subjects

Xiuzhen Li

Publications and source records attributed to Xiuzhen Li.

13 recordsLinked to original sources

PubMed2006

[Long-term effects of different planting proportion on forest landscape in Great Hing' anling Mountains after the catastrophic fire in 1987].

With LANDIS model, this paper simulated the long-term dynamics of 100% larch (P1) 70% larch and 30% Mongolian Scotch pine (P2), 50% larch and 50% Mongolian Scotch pine (P3), 30% larch and 70% Mongolian Scotch pine (P4), and 100% Mongolian Scotch pine (P5) in the Tuqiang Forest Bureau at the northern slope of Great Hing' anling Mountains after the catastrophic fire in 1987, taking the forest under natural regeneration as the reference. The results showed that at the early, medium, and late stages of succession, different planting proportion all had significant effects on the abundance of larch, Mongolian Scotch pine, and white birch. The abundance of larch increased with time,while that of Mongolian Scotch pine was in a converse way. Larch and Mongolian Scotch pine had an increased abundance with their increasing planting proportion, but the abundance of white birch was higher under natural regeneration than under different proportions of planting. The abundance of white birch was positively affected by the planting proportions of larch and Mongolian Scotch pine. As for the total abundance of larch and Mongolian Scotch pine, it had no significant difference under P2, P3 and P4, but was higher than that under P1 and P5, indicating that individual-species planting should not be used in the forest landscape.

Betula↗

PubMed2006

[Research advances in depth of edge influence of landscape boundary].

Depth of edge influence of landscape boundary is an important component of landscape boundary research, and also, the hotspot of ecological research at home and abroad. This paper summarized the recent decades' research advances abroad in depth of edge influence, including quantitative methods, depth of edge influence on abiotic and biotic factors, and affecting factors on depth of edge influence. The studies on depth of edge influence in our country were also discussed,with the development trend prospected.

Conservation of Natural Resources↗

PubMed2006

[Effects of different sampling modes on the results of vegetation ordination analysis].

The relationships between plant and environment are an important topic in community ecology. To study these relationships, quadrate is often used to sample vegetation and environmental data, and ordination techniques are used to analyze the data. However, the size and shape of quadrate considerably affect the ordination results. To understand this effect remains a research item for various vegetation and environmental data settings. This paper studied the effects of different sampling quadrate (size and shape) on the results obtained from three common ordination techniques (CA, DCA and CCA). We did this by sampling the same transect in forest form map six times, using six different quadrates (0.5 km x 0.5 km, 0.5 km x 2 km, 2 km x 0.5 km, 1 km x 1 km, 1 km x 4 km, 2 km x 2 km). The results showed that large rectangle quadrate could capture greater percent variance of species data and more information about rare and unique species than small square quadrate. All sizes and shapes of quadrate used in this study had little effect on the dominant species. The captured soil information was sensitive both to the size and to the shape of quadrate, and the information of slope, longitude and latitude was sensitive to the change of quadrate size. Slope position, altitude, temperature and precipitation were sensitive to the change of quadrate shape. Large quadrate reduced the importance of altitude, temperature and precipitation while increased the importance of exposure, but these environmental factors appeared to be important in small quadrate sampling.

Conservation of Natural Resources↗

PubMed2006

[A comparison of water balance in small basins with different landscape pattern in the upper reaches of Minjiang River].

This paper studied the effects of landscape pattern (land cover types, altitude, slope, aspect, patch density and maximum patch index) on the elements of water balance (precipitation, evapotranspiration, and runoff) in two small basins (Zhenjiangguan River and Heishui River) in the upper reaches of Minjiang River during 1988 -2002. Based on the spatial distribution of mean annual precipitation and evapotranspiration as well as the mean annual runoff on different land cover (woodland, grassland and cropland) during 1988-2002, the relationships of landscape pattern with water balance was approached, and the results showed that in these two basins, the precipitation, evapotranspiration / precipitation ratio, and runoff / precipitation ratio had a greater difference with the altitude, slope, and aspect of woodland, and grassland had a similar hydrological effect as woodland. On the farmland of Heishui River basin, which was distributed in dry valley, evapotranspiration was much higher than precipitation. This abnormal water balance was caused by the arid valley climate in the upper reaches of Minjiang River but not the landscape pattern of farmland, being totally different with that in Zhenjiangguan River basin.

China↗

PubMed2005

[GIS-based forest fire risk zone mapping in Daxing'an Mountains].

In this study, the Yuying and Fendou forest farms of Tuqiang Forest Bureau in Daxing'an Mountains were chosen as test areas, and their vegetation type, altitude, slop, aspect, and settlement buffer were selected as the main forest fire factors. The circumstances of forest fire risk were quantified by the factor-weights union method with the support of GIS. Four classes of forest fire risk ranging from low to extreme were generated. The none-, low, moderate, high, and extremely high fire risk zones accounted for 0.37%, 0.63%, 38.67%, 58.63% and 1.70%, respectively, which was in corresponding with normal distribution. About 60.33% of the test areas were predicted to be upper moderate risk zones, indicating that the forest fire management task in these areas is super onerous. There was an obvious regional difference in the distribution of forest fire risk zones, being higher in the center and lower around the center, and the difference in fire factors was also obvious. The GIS-based forest fire risk model of test areas strongly cohered with the actual fire-affected sites in 1987, which suggested that the forest fire risk zone mapping had a higher reliability, and could be used as the reference and guidance of forest fire management.

China↗

PubMed2004

[Spatially explicit landscape model-LANDIS I. Mechanism].

Spatially explicit landscape models are the models that spatially explicitly simulate the ecological processes at landscape scale on heterogeneous landscape. LANDIS is a spatially explicit landscape model of forest landscape disturbance, succession and management. By recording the absence/presence of species in terms of 10-yr age cohorts at site level, the semi-quantitative description of fire and windthrow disturbances, and the representation of age-cohorts by bit-wise array, it is possible for LANDIS to simulate the ecological processes at species, site and landscape level. We addressed in detail the approaches used in simulating seed dispersal, disturbances of fire and windthrow, and harvesting. The deficiencies of the model were also discussed to provide feedback for model development.

Biodiversity↗

PubMed2004

[Consistency between neutral landscape models and real landscape].

Neutral landscape models (NLM) can provide standards against real landscapes, and are used to describe landscape pattern and process in the past few decades. In this paper, the neutral landscape models RULE and SimMap were tested against a real landscape, and a set of landscape metrics were used to quantify the spatial characteristics of real and simulated patterns. Measurements of some metrics (total number of patches, total perimeter, average patch area, aggregation index, contagion and lacunarity) suggested that definite level of consistency between NLM-generated maps and real landscape did exist at landscape or class levels. But, there were also some metrics, such as corrected patch perimeter-area ratio, fractal double-logged and edge distribution evenness, which didn't show any agreement between the generated maps and real landscape. In all, each NLM had its own strength in representing real landscape, but none of them was perfect.

Conservation of Natural Resources↗

PubMed2004

[Sensitivity analysis in ecological modeling].

Sensitivity analysis is used to qualitatively or quantitatively apportion the variation of model output to different source of variation. It is a very useful tool in model parameterization and calibration, and has important ecological significance by identifying the governing factors for a certain ecological process simulated. There are two schools of sensitivity analysis, local sensitivity analysis and global sensitivity analysis. The former examines the local response of the output(s) by varying input parameters one at a time, holding other parameters to a central value; and the latter examines the global response (averaged over the variation of all the parameters) of model output(s) by exploring a finite (or even an infinite) region. Since it is very easy to conduct local sensitivity analysis, it is very popular in ecological models. However, local sensitivity analysis is not computationally effective, because it can only get the sensitivity of a single parameter at a time. It can not take into consideration the effect of interaction of different parameters. Additionally, the value of other parameters will affect the sensitivity of the parameter specified. In view of this, global sensitivity analysis is increasingly preferred to local sensitivity in recent years. However, for most of the ecological modeling study published in Chinese, only local sensitivity analysis is conducted. To provide a toolbox of alternative sensitivity analysis algorithms for ecological model development in future study, we reviewed the main methods of both local sensitivity analysis and global sensitivity analysis, including one at a time method, multivariate regression, Morris' method, Sobol's method, Fourier Amplitude Sensitivity Analysis, and Extended Fourier Amplitude Sensitivity Analysis. Based on the state-of-the-art research on sensitivity analysis, the sensitivity of the interaction between two or more than two model parameters, the sensitivity of common model parameters in a set of models, and the sensitivity analysis in spatially explicit landscape model simulation were identified as the key areas and difficulties of future study on sensitivity analysis in ecological modeling.

Ecology↗

PubMed2004

[Depth of edge influence on agriculture-forestry boundary in arid valley of upper reaches of Minjiang River, China].

By using moving split-window techniques (MSWT), this study estimated how far the edge effects penetrated the forest and agricultural fields in the arid valley of upper reaches of Minjiang River, southwestern China. Its aim was to provide general information on vegetation along edge to interior gradients in order to assist in interpretation and prediction of biological phenomena associated with agriculture-forestry boundary, and to improve current management practices in such areas. Three types of boundaries (10 transects) were investigated and sampled. The results showed that when the window width reached 6-10, the change of the SED curve on the graph tended to become stable, and one or two peaks occurred. The depth of edge influence was clearly different for different types of boundaries, and could be estimated within 50 m from the edge to interior. The depth of edge influence (DEI) on vegetation diversity almost varied between 12-30 m, mainly depending on the patch type, topography and microclimate, but seldom on slope orientation. Of the 6 forest transects in the three types of boundaries, the DEI was detected only in the forest part transects M2 and M6, but almost detectable in the agricultural part of all transects. MSWT was considered to be a useful tool for characterizing edge dynamics if enough data was available, and became a simple and powerful technique for analyzing the boundary. The results will provide further knowledge for understanding the interaction between forestry and agriculture in the arid valley.

China↗

PubMed2004

[Application of spatially explicit landscape model in soil loss study in Huzhong area].

Universal Soil Loss Equation (USLE) has been widely used to estimate the average annual soil loss. In most of the previous work on soil loss evaluation on forestland, cover management factor was calculated from the static forest landscape. The advent of spatially explicit forest landscape model in the last decade, which explicitly simulates the forest succession dynamics under natural and anthropogenic disturbances (fire, wind, harvest and so on) on heterogeneous landscape, makes it possible to take into consideration the change of forest cover, and to dynamically simulate the soil loss in different year (e.g. 10 years and 20 years after current year). In this study, we linked a spatially explicit landscape model (LANDIS) with USLE to simulate the soil loss dynamics under two scenarios: fire and no harvest, fire and harvest. We also simulated the soil loss with no fire and no harvest as a control. The results showed that soil loss varied periodically with simulation year, and the amplitude of change was the lowest under the control scenario and the highest under the fire and no harvest scenario. The effect of harvest on soil loss could not be easily identified on the map; however, the cumulative effect of harvest on soil loss was larger than that of fire. Decreasing the harvest area and the percent of bare soil increased by harvest could significantly reduce soil loss, but had no significant effects on the dynamic of soil loss. Although harvest increased the annual soil loss, it tended to decrease the variability of soil loss between different simulation years.

China↗

PubMed2003

[A review on road ecology].

Roads are a widespread and increasing feature of most landscapes, and have great ecological effects, e.g., increased mortality of animals and plants and habitat loss from road construction, alteration of the physical and chemical environment, and changes in roadsides vegetation. The great impact on animal population includes road-kills, limiting population, road avoidance causing home arrange shift, modification of movement pattern and barrier effect subdividing habitat and populations. Roads alter landscape spatial pattern and interrupt horizontal ecological flows strongly. These impacts can be assayed by indices of road density, road-effect zone and road location. Furthermore, important applications of road ecology to planning, conservation and management are essential and potential. Road ecology presents us a surprising frontier of ecology.

Animals↗

PubMed2003

[Spatial diversity index analysis on wildlife habitat pattern change in the Liaohe Delta].

Based on the study of land cover change in the Liaohe Delta with GIS and RS, the wildlife habitat pattern was described quantitatively, and the pattern change between 1988 and 1998 was analyzed with spatial diversity index. The results showed that the wildlife habitat pattern had an obvious change during the ten years caused by natural and human disturbance. The area of suitable habitat(Sd > or = 0.35) was becoming smaller and more fragmented, with a deteriorated quality. It was proved that spatial diversity index could reflect the habitat suitability of wildlife, and describe the habitat spatial pattern explicitly. This study would provide a scientific basis for protecting wild animals and their habitats.

Animals↗

PubMed2003

[Scaling effects on landscape pattern indices].

The methods of spatial data aggregation based on majority and random rules were used in this study to reveal the scaling effects on landscape pattern in a classified TM imagery with 8 land cover types. For the majority rule-based aggregations, the proportion of most common cover types increased slowly, while that of less common cover types decreased rapidly with increasing grain. For random rule-based aggregation, each cover remained its original area on the aggregated maps. The largest patch sizes of shrub decreased, and those of the others increased in the majority rule-based aggregations with increasing scales. For random rule, the largest patch size of water (smallest cover type) decreased, but that of the others increased. The smallest patch size of each cover type was equal to the square of grain sizes. The average patch size of each cover type increased with increasing scales. However, the average patch size of dominant cover types increased rapidly in majority rule-based aggregations, while that of less common cover types increased rapidly in random rule-based aggregation. The patch count of each cover types decreased substantially with increasing grain. Random rule-based aggregation made landscape more fragmented and remained more patches. The diversity decreased in majority rule-based aggregation, and maintained its original value in random rule-based aggregation with increasing scales. Aggregation indices decreased with increasing map and measurement resolution, and the landscape became more aggregated in majority rule-based aggregation. However, under fixed measurement resolution (e.g., 30 m), aggregation indices increased and cover types were more clustered with increasing resolution. Moran's I decreased rapidly with increasing measurement and map resolution, and each cover type tended to be arranged randomly and independently in space. However, under fixed measurement resolution (e.g., 30 m), Moran's I increased and cover types were more clustered on aggregated maps than on original map with increasing map resolution.

Ecosystem↗